298 MICRO-ORGANISMS AND DISEASE [chap. 



a whole is lost ; the affected mucosa itself becomes necrosed 

 and changed into a whitish-grey coagulated mass, in which 

 fibrin, a close network of threads and septa, and in the 

 superficial parts lymph cells, may be recognised, this ne- 

 crosed or coagulated portion forming the diphtheritic mem- 

 brane ; close to that part which comprises the necrosed 

 mucosa the outlines of blood-vessels filled with stagnated 

 and coagulated blood, and extravasated blood, as also 

 dense infiltration with lymph cells, may be recognised. 

 When the process continues into the depth and breadth, 

 this inflamed portion also becomes necrosed, and a part of 

 the diphtheritic membrane. After the process passes the 

 acme, the inflamed tissue, not necrosed by the exudation, 

 gradually detaches the diphtheritic membrane above it, and 

 an ulcer is left behind, which, like other healing ulcers, 

 gradually contracts and becomes covered with healthy 

 membrane and epithelium. 



A section through a diphtheritic membrane shows a few 

 nuclei in a dense, more or less fibrinous, reticulated or 

 hyaline matrix, more or less ill-preserved ; some of these 

 take the staining, i.e. are not dead ; in others already dead 

 the outlines can be barely recognised. In the superficial 

 parts of the diphtheritic membranes a number of larger or 

 smaller loculi are always seen, which are filled with clumps 

 of bacteria (see illustration). These clumps of bacteria are 

 of various kinds : generally staphylococci and at least two 

 kinds of streptococci, thick and long septic bacilli, and 

 groups of minute bacilli which we will call the diphtheria 

 bacilli. These latter are found in larger and smaller masses 

 on the surface, forming sometimes a continuous layer ; in 

 some cases sections show that in the middle, and occasion- 

 ally, but rarely, even in the deep parts, they are the only 

 bacteria present ; here they are in small clusters, or they 



